The Pizza Slices and Cokes
29) Andy and Lonnie were trying to remember how much the cokes and pizza
slices were at the corner restaurant. Recently, they had bought 2 cokes and
5 pizza slices for $16.85; and a couple days earlier, they bought 4 cokes
and 3 pizza slices for $13.05. What is the cost of each pizza slice and
each coke?
For this problem, we are going to use two different variables.
x = coke
y = pizza slice
2x + 5y = 16.85
4x + 3y = 13.05
We now want to eliminate one of the variables by multiplying the top
formula by -2, so that the x's will cancel out:
-4x -10y = -33.70
4x + 3y = 13.05
----------------
-7y = -20.65
y = 2.95
Now that we know the value of y, we can plug that back into the formula
to find the value for x, as follows:
(2x + 5y = 16.85)
2x + 14.75 = 16.85
2x = 2.10
x = 1.05
Each pizza slice is $2.95, and each coke is $1.05.